With the rapid development of mobile communication service, high-quality communication service is required in secluded places among mountains, remote islands, shadow areas in metropolitan areas, subways, tunnels and apartments which have a low need for communication service and to which mobile communication service has not been sufficiently provided to date. However, a communication service provider making a large investment in increasing base stations in shadow areas may deteriorate the business balance of the communication service provider and may cause losses attributable to the inefficiency of the large investment at the national level in the worst case. A ‘repeater system’ capable of realizing high communication quality and improving a service coverage at low cost has been utilized as a method of dealing with such a problem.
Recently, as the period when one person has one mobile phone has come, scientific technology fields, which are basis thereof, may representatively include the introduction of the concept of cellular communication, the development of wireless transmission technology (commercialization of Code Division Multiple Access: CDMA), and the development of optical transmission technology.
The concept of cellular communication is intended to solve the problem of inefficient communication capacity and quality attributable to a limited frequency spectrum, which is the largest restriction imposed on wireless communication, by dividing an entire area into units called cells and by improving efficiency of frequency reuse, thus providing an opportunity to develop wireless mobile communication. The development of wireless transmission technology provides an opportunity to develop wireless mobile communication from the standpoint of the digitization of a wireless communication system.
Methods of extending cell coverage by introducing repeaters to a mobile communication system have been attempted in various fields. For example, Working Group 4 (WG4) of Wireless World Research Forum (WWRF) has attempted to extend cell coverage and improve a transfer rate by introducing repeaters to a mobile communication system. For this purpose, WWRF proposed to arrange grating-shaped repeaters in a Manhattan city scenario in which metropolitan situations are considered, and also proposed a transmission frame structure suitable for the grating-shaped repeaters.
Further, WWRF proposed a cooperative relaying method using several stages of repeaters in “Technologies for the wireless future chapter 6, WWRF2005”, and also analyzed the performance of the cooperative relaying method. However, such an attempt reaches a level in which the utility of repeaters in a classical meaning is merely regulated, so that estimation implying that it is difficult to regard such an attempt as a new idea and to predict great usefulness thereof is dominant.
In addition, WINNER Project composed of 43 unions, such as a plurality of businesses and universities in Europe, is also conducting research for introducing repeaters to an existing mobile communication network and realizing the improvement of performance. The structure of “Wireless multi-hop mesh network” proposed by WINNER is intended to secure redundancy by maintaining topology between repeaters in a mesh structure and to secure transmission efficiency by maintaining a connection between each repeater and a terminal in a Point-to-Multi-Point (PMP) structure (“Description of identified new relay based radio network deployment concepts and first assessment by comparison against benchmarks of well known deployment concepts using enhanced radio interface technologies”, IST-2003-507581 WINNER D3.1).
In addition, a Time Division Duplex (TDD)-based Heterogeneous Relay Node (HERN) system has presented the typical meaning of the allocation of time slots and frequency resources, but does not mention a detailed algorithm thereof. Further, the system proposed both Initiative Marketing Digital Radio (IMDR), which is a relaying method between terminals performed in consideration of multi-user diversity, and a coded bi-directional relaying method, which shortens a relaying time for repeaters, in “Definition and assessment of relay based cellular deployment concepts for future radio scenarios considering 1st protocol characteristics, IST-2003-507581 WINNER D3.4”. However, the system does not present a method of arranging repeaters to eliminate interference between cells and a resource allocation algorithm related thereto.
Further, a current mobile communication network is configured in the form of six hexagonal cells around a single cell in the case of a 3-sector base station, as shown in FIG. 1. In such a cell structure, average capacity that can be provided by a single base station is about 55% of the maximum capacity of the base station due to interference signals from adjacent base stations. That is, in the case of a base station capable of providing a maximum capacity of 10 Mbps, mobile stations uniformly distributed around the base station are provided with a service capacity of about 5.5 Mbps on the average in the current situation, and thus capacity efficiency is low.